Push model prefix only if existing

Author: alvarobartt

backends/candle/src/models/flash_qwen2.rs

@@ -264,7 +264,15 @@ impl FlashQwen2Model {
             ModelType::Embedding(pool) => pool,
         };
 
-        let vb = vb.pp("model");
+        // Pushing the prefix for `model` is apparently only required if the model architecture is
+        // ForCausalLM as it contains the `lm_head`, other than that, the `model` key won't be
+        // present e.g. a model without the `model` key as it's a `Qwen2Model` instance not a
+        // `Qwen2ModelForCausalLM` is https://huggingface.co/mims-harvard/ToolRAG-T1-GTE-Qwen2-1.5B
+        let vb = if vb.contains_tensor("model.embed_tokens.weight") {
+            vb.pp("model")
+        } else {
+            vb
+        };
 
         let embeddings = Embedding::new(
             vb.pp("embed_tokens")